She still works for the restaurant AFTER they found she posted the receipt in violation of company policy. That makes the restaurant complicit in slandering the customer. Let’s go to trial and sort it out.
I agree hiring the waitress back makes the restaurant complicit in the slander, providing there is strong evidence, more than circumstantial, that she wrote the slur.
She was probably hired back out of fear that the Rev Al and Jesse Hijackson would descend on them if they didn’t.